FOREGUT ANATOMY OF CRASSISPIRINE GASTROPODS 

 Guraleus costatus (Hedley, 1922) 



(Fig. 28b) 



Unfortunately, the specimen was sectioned nearly transversely and 

 an illustration of it comparable with the other species was not 

 possible. 



Rhynchodeum and proboscis 



The rhynchodeal sphincter is small and anteriorly located. The 

 epithelium of the anterior part of the rhynchodeal cavity is glandular, 

 whilst that of the posterior rhynchodeum is nonglandular and con- 

 tinuous with that of the proboscis wall. The non-glandular posterior 

 part of the rhynchodeum is very thin and attached by numerous 

 muscle fibres to the body wall and probably cannot be everted. The 

 rhynchostome is narrow. 



The proboscis is very long and coiled, more than twice as long as 

 the rhynchodeal cavity. It is very thick at the base but narrows 

 towards the tip (diameter of 0.44 mm at the base, but only 0.08 at the 

 tip). The proboscis walls are thin, comprising less than 17c of the 

 proboscis diameter at its base. The mouth is very narrow. A very 

 small, anterior buccal tube sphincter, lies in front of a small, sac-like 

 enlargement of the buccal tube. The epithelium, lining the enlarge- 

 ment is similar to that of the rest of the buccal tube. A single tooth 

 was seen in the enlargement. There is large intermediate sphincter, 

 situated approximately midway down the proboscis. The buccal 

 tube is very narrow anteriorly, but broad in the posterior part of the 

 proboscis. Its walls are very thin and highly folded. 



Buccal mass and oesophagus 



The buccal mass lies within the base of the proboscis, with thick 

 walls and rather broad inner cavity, and showing no curvature. There 

 are large, extensible, buccal lips, which can be inverted inside the 

 cavity. The oesophagus is slightly elongated between buccal mass 

 and nerve ring and forms a short loop. There is no buccal sac. The 



81 



salivary ducts open into the buccal cavity on both sides of the 

 opening of the radular diverticulum. 



Glands 



The salivary glands are small, paired and acinous. The venom gland 

 changes abruptly in histology after passing through the nerve ring. 

 The duct is very narrow, unciliated and opens at the border between 

 the buccal mass and oesophagus. The muscular bulb is large, the wall 

 is formed of two equal layers of longitudinal fibres, divided by a 

 connective tissue layer, with a thin, innermost layer of circular 

 muscle. 



Odontophore and radula 



The odontophore is rather large with a pair of unfused cartilages. 

 The radula consists of marginal teeth of the wishbone type (Fig. 

 28b). Each tooth has a robust and pointed major limb with a straight, 

 blade-like leading edge. The secondary limb is long and slender and 

 attached to the major limb near the distal tip. The marginal teeth are 

 very long, ca. 1 05um ( 1 .4% of SL, 4.2% AL). 



Burchia spectabilis Sysoev & Taylor, 1997 



(Fig. 29) 



See Sysoev & Taylor (1997, fig. 3) 



Rhynchodeum and proboscis 



The rhynchodeal sphincter is very large, and located slightly to the 

 posterior. The anterior one third of the rhynchodeal cavity possesses 

 a very tall, glandular, folded epithelium formed of large cells. The 

 epithelium of the posterior two thirds of the rhynchodeum is con- 

 tinuous with that of the proboscis wall and is low, cubic and 

 non-glandular. This indicates, that the greater part of the rhynchodeal 

 lining is involved in proboscis protraction. The rhynchostome is 

 narrow. 



asgm 



Fig. 29 Burchia spectabilis Sysoev & Taylor, 1997. Semidiagrammatic longitudinal section of the foregut (salivary ducts not shown). 



